Metric Tons Of Carbon Research Articles

Development of an end-use model for analyzing policy options to reduce greenhouse gas emissions

An end-use energy model is presented for assessing policy options to reduce greenhouse gas emissions. This model evaluates the effects of imposing a carbon tax on various carbon-emitting technologies in order to reduce CO/sub 2/ emissions. It also estimates the effects of a carbon tax in combination with subsidies. The problem can be formulated in terms of two-level mathematical programming. An algorithm is proposed and applied to estimate Japanese CO/sub 2/ emissions. The conditions under which energy-saving technologies would be selected are analyzed using various carbon tax rates and subsidies, and the reduction of CO/sub 2/ emissions is calculated based on the introduction of such technologies. It is found that a low carbon tax such as 3000 yen per metric ton of carbon (tC) is insufficient to stabilize CO/sub 2/ emissions at the 1990 level in Japan, and that a tax of 30000 yen/tC would be necessary. However, the proposed algorithm shows that total emissions in Japan in the year 2000 can be stabilized at the 1990 level with a tax of 3000 yen/tC if the tax revenues are used to subsidize the introduction of energy-saving technologies.

Projected regional impacts of appliance efficiency standards for the US residential sector

Minimum efficiency standards for residential appliances have been implemented in the US for a large number of residential end-uses. This analysis assesses the potential energy, dollar, and carbon impacts of those standards at the state and national levels. We explicitly account for improvements in efficiency likely to occur in the absence of standards, but because our method for characterizing these exogenous improvements probably overestimates them, both the energy and cost savings presented in this article represent lower bounds to the true benefits. Cumulative present-valued dollar savings after subtracting out the additional cost of the more efficient equipment are about $30 billion from 1990 to 2010. Each dollar of federal expenditure on implementing the standards will contribute $165 of net present-valued savings to the US economy over the 1990 to 2010 period. Average benefit/cost ratios for these standards are about 3.5 for the US as a whole. Projected carbon reductions are approximately 9 million metric tons of carbon per year in the years from 2000 to 2010. Because these standards save energy at a cost less than the price of that energy, the resulting carbon emission reductions are achieved at negative net cost to society.

Sensitivity of boreal forest carbon balance to soil thaw

We used eddy covariance; gas-exchange chambers; radiocarbon analysis; wood, moss, and soil inventories; and laboratory incubations to measure the carbon balance of a 120-year-old black spruce forest in Manitoba, Canada. The site lost 0.3 +/- 0.5 metric ton of carbon per hectare per year (ton C ha-1 year-1) from 1994 to 1997, with a gain of 0.6 +/- 0.2 ton C ha-1 year-1 in moss and wood offset by a loss of 0.8 +/- 0.5 ton C ha-1 year-1 from the soil. The soil remained frozen most of the year, and the decomposition of organic matter in the soil increased 10-fold upon thawing. The stability of the soil carbon pool ( approximately 150 tons C ha-1) appears sensitive to the depth and duration of thaw, and climatic changes that promote thaw are likely to cause a net efflux of carbon dioxide from the site.

8 Genetic, Molecular, and Morphological Analysis of Compound Leaf Development

Leaves, the plant organs responsible for capturing and converting most of the 170 billion metric tons of carbon fixed globally each year, can be broadly grouped into two morphological categories: simple and compound. Although simple-leaved species such as corn and Arabidopsis have traditionally been favored model systems for studying leaf development, recent years have seen an increase in genetic and molecular studies of compound leaf development. Two compound-leaved species in particular have emerged as model systems: tomato and pea. A variety of mutations which alter leaf morphology in these species have been described, and analyses of these mutations have allowed the construction of testable models of leaf development. Also, the knotted-like homeobox (KNOX) genes, which were originally discovered as regulators of meristem function, now appear to have a role in compound leaf development. In addition to the recent genetic and molecular analyses of tomato and pea, insight into the nature of compound leaf development may be gained through the study of (a) heteroblasty and heterophylly, phenomena in which a range of leaf forms can be produced by a single shoot, and (b) the evolutionary origins of compound leaves.

Effects of darkness on multi‐excitation in vivo fluorescence and survival in a marine diatom

Surveys of the California Current System in 1993 revealed high concentrations of photosynthetic pigment biomass at ∼200‐m depth, well below the euphotic zone. The deep fluorescence feature contained an estimated 2.2 × 104 metric tons of carbon and contained ∼2.5 times the amount of chlorophyll observed in surface waters directly above it. Deep phytoplankton assemblages may be a signature of water mass subduction, suggesting the possibility of using phytoplankton as water mass tracers. These field observations led to a laboratory study of the fluorescence characteristics of autotrophic cells as possible indices of acclimation to extended periods of darkness. In vivo multiexcitation Chl a fluorescence of the diatom Thalassiosira weissflogii was monitored for 2 months of total darkness. Numbers of living and dead cells were determined using the vital stain fluorescein diacetate (FDA). By the end of the dark incubation period, in vivo Chl a fluorescence and fluorescence per cell had leveled off to ∼45% and 65% of initial values, respectively. The contribution of accessory pigments to Chl a fluorescence, expressed as multiexcitation fluorescence ratios, was higher in the dark than prior to transfer to darkness but showed no significant changes during 2 months of darkness. The FDA assay indicated that ∼85% of the cells were alive for at least the first 3 weeks during the first dark experiment and for the entire 2 months of second dark incubation. Cell numbers decreased to 65% of initial values and then grew exponentially upon reexposure to a light: dark photoperiod. Our results for T. weissflogii suggest that extended light limitation of photosynthesis does not preclude the survival of subducted phytoplankton assemblages and the consequent accumulation of Chl a at depths below the euphotic zone. If these results extend to natural assemblages, it is not possible to estimate advective time scales based on a maximum persistence time of pigment fluorescence below the euphotic zone. Nevertheless, the deep phytoplankton assemblage we observed provides evidence for water mass subduction and suggests that large, intermittent pulses of phytoplankton carbon are a part of cross‐shelf exchange and vertical flux from surface waters to depth in this region.

The Carbon Crop

Anne Simon Moffat's spotlight on carbon sequestration through forest regeneration (Research News, [18 July, p. 315][1]) is most welcome, but needs explicit reference to a key driver in the carbon ecosystem: paying for it. Carbon sequestration through forest or peat restoration is simply growing a carbon crop. The socioeconomics of farming apply. If carbon is to be sequestered massively and permanently through the restoration of forests, a process both biologically straightforward and well understood for decades, then someone has to buy the crop. We must close the sociopolitical loop and internalize environmental costs—the polluter pays. Those of us structuring carbon sequestration projects hope that the U.S. government's role in Kyoto, Japan, in December 1997 will achieve a market force for the carbon crop. We already have the technology, the protocols, and the will to crank up massive mitigative regeneration of tropical and mid-latitude forests. A carbon generator can lower its impact by buying a virtual or real mechanical scrubber, or it can buy a green scrubber, that is, regenerate forest. Why bother with trees? The sequestered green carbon plays an enormous “other” role besides hauling the carbon out of the air. Wildlands and tree-rich agroecosystems generate an array of goods and services—from water control to ecotourism, biodiversity prospecting, education, orange juice, carbon parked in valuable furniture, and more—and the storage of up to several hundred metric tons of carbon per hectare. The payment for the carbon scrubbing service achieved through forest restoration and the establishment of woody plantations can be the capital investment that sets the living factory in place. Later, the other goods and services may well generate sufficient income for maintenance and favorable competition with other crops that store less carbon. There is also a second, hidden process. The paying polluter wants an assurance that the purchased carbon will stay put. The wildland biodiversity and ecosystem development industry is that assurance. [1]: /lookup/doi/10.1126/science.277.5324.315

GREENHOUSE GASES FROM DEFORESTATION IN BRAZILIAN AMAZONIA: NET COMMITTED EMISSIONS

Deforestation in Brazilian Amazonia is a significant source of greenhouse gases today and, with almost 90% of the originally forested area still uncleared, is a very large potential source of future emissions. The 1990 rate of loss of forest (13.8 × 103 km2/year) and cerrado savanna (approximately 5 × 103 km2/year) was responsible for releasing approximately 261 × 106 metric tons of carbon (106 t C) in the form of CO2, or 274–285 × 106 t of CO2-equivalent C considering IPCC 1994 global warming potentials for trace gases over a 100-year horizon. These calculations consider conversion to a landscape of agriculture, productive pasture, degraded pasture, secondary forest, and regenerated forest in the proportions corresponding to the equilibrium condition implied by current land-use patterns. Emissions are expressed as ‘net committed emissions’, or the gases released over a period of years as the carbon stock in each hectare deforested approaches a new equilibrium in the landscape that replaces the original forest. For low and high trace gas scenarios, respectively, 1990 clearing produced net committed emissions (in 106 t of gas) of 957–958 for CO2, 1.10–1.42 for CH4, 28–35 for CO, 0.06–0.16 for N2O, 0.74–0.74 for NOx and 0.58–1.16 for non-methane hydrocarbons.

Quantifying urban forest structure, function, and value: the Chicago Urban Forest Climate Project

This paper is a review of research in Chicago that linked analyses of vegetation structure with forest functions and values. During 1991, the regions trees removed an estimated 5575 metric tons of air pollutants, providing air cleansing worth 9.2 million. Each year they sequester an estimated 315 800 metric tons of carbon. Increasing tree cover 10% or planting about three trees per building lot saves annual heating and cooling costs by an estimated 50 to 90 per dwelling unit because of increased shade, lower summertime air temperatures, and reduced neighborhood wind speeds once the trees mature. The net present value of the services trees provide is estimated as 402 per planted tree. The present value of long-term benefits is more than twice the present value of costs.

Exchange of Carbon Dioxide by a Deciduous Forest: Response to Interannual Climate Variability

The annual net uptake of CO 2 by a deciduous forest in New England varied from 1.4 to 2.8 metric tons of carbon per hectare between 1991 and 1995. Carbon sequestration was higher than average in 1991 because of increased photosynthesis and in 1995 because of decreased respiration. Interannual shifts in photosynthesis were associated with the timing of leaf expansion and senescence. Shifts in annual respiration were associated with anomalies in soil temperature, deep snow in winter, and drought in summer. If this ecosystem is typical of northern biomes, interannual climate variations on seasonal time scales may modify annual CO 2 exchange in the Northern Hemisphere by 1 gigaton of carbon or more each year.

The role of phytoplankton photosynthesis in global biogeochemical cycles

Phytoplankton biomass in the world's oceans amounts to only ∽1-2% of the total global plant carbon, yet these organisms fix between 30 and 50 billion metric tons of carbon annually, which is about 40% of the total. On geological time scales there is profound evidence of the importance of phytoplankton photosynthesis in biogeochemical cycles. It is generally assumed that present phytoplankton productivity is in a quasi steady-state (on the time scale of decades). However, in a global context, the stability of oceanic photosynthetic processes is dependent on the physical circulation of the upper ocean and is therefore strongly influenced by the atmosphere. The net flux of atmospheric radiation is critical to determining the depth of the upper mixed layer and the vertical fluxes of nutrients. These latter two parameters are keys to determining the intensity, and spatial and temporal distributions of phytoplankton blooms. Atmospheric radiation budgets are not in steady-state. Driven largely by anthropogenic activities in the 20th century, increased levels of IR- absorbing gases such as CO2, CH4 and CFC's and NOx will potentially increase atmospheric temperatures on a global scale. The atmospheric radiation budget can affect phytoplankton photosynthesis directly and indirectly. Increased temperature differences between the continents and oceans have been implicated in higher wind stresses at the ocean margins. Increased wind speeds can lead to higher nutrient fluxes. Throughout most of the central oceans, nitrate concentrations are sub-micromolar and there is strong evidence that the quantum efficiency of Photosystem II is impaired by nutrient stress. Higher nutrient fluxes would lead to both an increase in phytoplankton biomass and higher biomass-specific rates of carbon fixation. However, in the center of the ocean gyres, increased radiative heating could reduce the vertical flux of nutrients to the euphotic zone, and hence lead to a reduction in phytoplankton carbon fixation. Increased desertification in terrestrial ecosystems can lead to increased aeolean loadings of essential micronutrients, such as iron. An increased flux of aeolean micronutrients could fertilize nutrient-replete areas of the open ocean with limiting trace elements, thereby stimulating photosynthetic rates. The factors which limit phytoplankton biomass and photosynthesis are discussed and examined with regard to potential changes in the Earth climate system which can lead the oceans away from steady-state. While it is difficult to confidently deduce changes in either phytoplankton biomass or photosynthetic rates on decadal time scales, time-series analysis of ocean transparency data suggest long-term trends have occurred in the North Pacific Ocean in the 20th century. However, calculations of net carbon uptake by the oceans resulting from phytoplankton photosynthesis suggest that without a supply of nutrients external to the ocean, carbon fixation in the open ocean is not presently a significant sink for excess atmospheric CO2.

Soil organic matter must be restored to near original levels

Abstract Burning of fossil fuels globally helps put 3 billion metric tons of carbon into the atmosphere per year more than is removed by all carbon sinks. By far the best use of that carbon would be to arrange sufficient extra plant growth and then transfer that plant growth into new stable soil organic matter. Twenty or more years of such effort would immensely improve the soils of the world. Any fraction of it would help decrease the threat of global greenhouse warming. A great worldwide goal should be to increase levels of soil organic matter levels considerably. It should be possible. The most important research relating to soil organic matter is perhaps yet to be done. Elucidation of the regulators involved in the build‐up and decomposition processes of various types of soil organic matter deserves high priority. It should be possible to develop technologies where the regulators can be managed and controlled for the beneficial purpose of increasing levels of soil organic matter. The role of calcium i...

CURBING GLOBAL WARMING Clinton unveils ambitious action plan

At a White House ceremony last week, President Bill Clinton announced an ambitious plan to fight global warming using voluntary programs, government regulations, and increased support for renewable energy. Climate Change Action Plan is designed to return greenhouse gas emissions to 1990 levels by 2000. At the same time, it will expand markets for U.S. technologies and services, create jobs, and reduce the deficit, Clinton said. plan would reduce annual greenhouse gas emissions by the equivalent of 107 million metric tons of carbon below what they would otherwise be in 2000. plan includes 50 new or expanded programs that will each contribute to cutting greenhouse gas emissions. Many of them involve establishing public-private partnerships with key industries. plan meets the President's commitment made last spring to fulfill U.S. obligations under the Climate Convention signed in Brazil last year. The action plan reestablishes the U.S. as a world leader in protecting the ...

Net Exchange of CO 2 in a Mid-Latitude Forest

The eddy correlation method was used to measure the net ecosystem exchange of carbon dioxide continuously from April 1990 to December 1991 in a deciduous forest in central Massachusetts. The annual net uptake was 3.7 +/- 0.7 metric tons of carbon per hectare per year. Ecosystem respiration, calculated from the relation between nighttime exchange and soil temperature, was 7.4 metric tons of carbon per hectare per year, implying gross ecosystem production of 11.1 metric tons of carbon per hectare per year. The observed rate of accumulation of carbon reflects recovery from agricultural development in the 1800s. Carbon uptake rates were notably larger than those assumed for temperate forests in global carbon studies. Carbon storage in temperate forests can play an important role in determining future concentrations of atmospheric carbon dioxide.

Atmospheric Carbon Reduction by Urban Trees

Trees, because they sequester atmospheric carbon through their growth process and conserve energy in urban areas, have been suggested as one means to combat increasing levels of atmospheric carbon. Analysis of the urban forest in Oakland, California (21% tree cover), reveals a tree carbon storage level of 11·0 metric tons/hectare. Trees in the area of the 1991 fire in Oakland stored approximately 14 500 metric tons of carbon, 10% of the total amount stored by Oakland's urban forest. National urban forest carbon storage in the United States (28% tree cover) is estimated at between 350 and 750 million metric tons. Establishment of 10 million urban trees annually over the next 10 years is estimated to sequester and offset the production of 363 million metric tons of carbon over the next 50 years—less than 1% of the estimated carbon emissions in the United States over the same period. Advantages and limitations of managing urban trees to reduce atmospheric carbon are discussed.

CO EMISSION REDUCTIONS: U.S. programs to yield big cuts by 2000

The U.S. may come very close to stabilizing its carbon dioxide emissions at 1990 levels by the year 2000 without spending much additional money or instituting new programs. A new Administration analysis being circulated by the State Department claims that federal programs already in place will achieve a reduction in annual CO 2 emissions of from 87 million to 121 million metric tons of carbon by 2000. And efforts to reduce other greenhouse gases, such as methane and nitrous oxide, will bring annual reductions to between 125 million and 200 million metric tons of carbon equivalents—or about 7 to 11% less than what emissions would otherwise be. The State Department is using the document as the basis for its negotiating position at climate convention meetings at the United Nations this week. The U.S. and about 140 other nations are engaged in the sixth and final session to work out a climate convention to be signed at ...

Effects of Nitrogen Loading on Wetland Ecosystems with Particular Reference to Atmospheric Deposition

Wetlands fulfill an important role in global biogeochemical cycles. For example, they transfer to the atmosphere globally significant quantities of CH4 (60, 61) and reduced sulfur gases (127). Coastal marshes may function as net sinks for N20 (46). Because of the anaerobic nature of their soils, wetlands act as sinks for organic carbon. It has been estimated that wetlands once sequestered a net of 57 to 83 x 106 metric tons of carbon per year worldwide, but recent widespread drainage of wetland soils has shifted the carbon balance (7). Although this rate of carbon uptake is small in comparison to other global carbon fluxes, such as the annual release of carbon from combustion of fossil fuel (5-6 x 109 metric tons yr1) (112) or the net uptake of C02-C by the ocean (1.6 x 109 metric tons yr-1) (129), it is important when the net balance between large fluxes is considered, and it is certainly important over geologic time scales. Locally, wetlands function as habitats for wildlife, as flood control systems, as stabilizers and sinks for sediments, as storage reservoirs for water, and as biological filters that maintain water quality. For example, riparian

Photovoltaics and materials science: helping to meet the environmental imperatives of clean air and climate change

Human activity is altering the composition of the atmosphere in unprecedented ways. Fossil fuel combustion, which currently releases 5.6 billion metric tons of carbon annually, in combination with deforestation, has increased atmospheric concentrations of carbon dioxide 25% above pre-industrial levels. Carbon dioxide and other greenhouse gases trap infrared radiation from the earth altering its thermal balance. While carbon dioxide is anticipated to contribute about one-half of human induced global warming, the world energy sector is responsible for an estimated 57% of future global warming when contributions from additional combustion related pollutants are included. In order to stabilize atmospheric concentrations of carbon dioxide even at current elevated levels, computer models suggest the need to reduce emission rates by approximately 75%. Present patterns of energy use are also contributing to major air pollution problems. An analysis of policy options shows that a combination of vastly improved energy efficiency strategies and carbon free energy production technologies are essential to simultaneously slow the rate of global warming and improve air quality. This paper summarizes current knowledge of the greenhouse effect and its consequences, and examines how photovoltaic electricity can contribute to atmospheric stabilization goals. Some specific examples and strategies will be given that may accelerate the rate at which photovoltaic technologies can penetrate the market. Should these strategies succeed, it will have majot implications for materials science including increased attention to pollution problems associated with the manufacture of many promising photovoltaic technologies.

Solar strategies for escaping the greenhouse heat trap

Abstract Human-induced global climate change poses an immense potential threat to our society, and a challenge to our ingenuity. Fossil fuel combustion, which currently releases 5.6 billion metric tons of carbon annually, in combination with deforestation, has increased atmospheric concentrations of carbon dioxide 25% above pre-industrial levels. Carbon dioxide is estimated to contribute approximately one-half of the anthropogenic increase in the absorption of the Earth's IR radiation. The world energy sector is responsible for an estimated 57% of future global warming when contributions from additional combustion-related pollutants are included. To stabilize atmospheric concentrations of carbon dioxide even at current levels, models suggest the need to reduce emission rates by 75%. An analysis of policy options shows that a combination of vastly improved energy efficiency strategies and carbon-free energy production technologies will be essential to even slowing global warming. This paper summarizes our knowledge of the greenhouse effect and its consequences, and examines the contribution that solar electricity and other renewables can make toward atmospheric stabilization goals. Some specific examples and strategies, which may accelerate the rate at which solar technologies can penetrate the market, will be given.

Tropical wetlands as a carbon source

Wetlands have long been recognized as a carbon sink, and a suggestion has been made that this may have served in the past several centuries to balance out releases from reduction of forests in the world. Cultural exploitation of wetland areas, such as excavation during exploration for fossil fuel and minerals, draining for farming of grain and fiber and production of animal protein, invariably results in the oxidation of the carbon storage sink. Destructive wetland alterations which reduce or remove the vegetative cover also decrease the fixation of atmospheric carbon, thus resulting in a net carbon release from wetlands. Wetland excavation for peat extraction is estimated to oxidize 472 metric tons of stored carbon per 1000 metric tons of dry peat combusted, while 375 metric tons of carbon are released from one hectare of mangrove swamp cleared and dug out for fish pond construction. Increasing and widespread alterations of this nature convert wetlands to a carbon source and could therefore play a significant role in the global cycle of carbon.

Life, Death, and Energy of a Tree

This paper gives the first complete life table for a tree and a tropical plant (the palm Euterpe globosa, in Puerto Rico). There is rapid but declining mortality before the shoot from one in a million seeds reaches the canopy. Mean generation length (not the minimum length usually used) is 100 years. A new set of parameters measures age-specific energy flow. Young trees are most important in nutrient competition, and on 6000 m2 of ground one year-class reduces about one metric ton of carbon throughout its life. Independent estimates confirm aspects of both the life table and the energy table. The energetic cost of reproduction is about a sixth of the net production of an individual (1 percent of the gross production) and about 5 percent of the net production of the population. The realized fitness of E. globosa, as a species, is roughly comparable to that of Homo sapiens. ALTHOUGH THE STUDY OF SURVIVORSHIP has been an important part of animal ecology for 30 or 40 years, there are few studies on plants. Most of these are for herbs, although there are scattered reports of survivorship of seedlings or adults of trees (e.g., Hett and Loucks 1971; Cooper 1960) and shrubs (Roughton 1972). Harper (1967) and Sarukhan and Harper (1973) have reviewed life tables of